Concentration dependence of ionic relaxation in lithium doped polymer electrolytes

Abstract

This is an author produced version of a paper published in Journal of NonCrystalline Solids. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. AbstractA detailed impedance spectroscopy study at ambient temperature was carried out on polymer electrolytes based on low molecular weight poly(ethylene oxide) 400, poly(propylene oxide) 400 and a random copolymer of molecular weight 600, to which were added LiN(CF 3 SO 2 ) 2 (LiTFSI) salt. The ionic conductivity exhibits a maximum at intermediate salt concentrations and is significantly higher for poly(ethylene oxide) and the copolymer. A dielectric relaxation was found in a frequency region above the one, where the ion conductivity dominates the dielectric response, and below the region of the relaxations of the polymer host. The relaxation strength scales with ion concentration, as appropriate for an ion pair relaxation in systems above the glass transition. The frequency of this relaxation, multiplied by the relaxation strength, has been found to be proportional to the ion conductivity, and the relaxation has therefore been assigned to short-range ion pair motion in the polymer. It exhibits characteristics similar to conductivity relaxations in inorganic solid ion conductors, and is considered to be due to the same species that give rise to the ion conductivity.

Ionic conductivity and dielectric behavior of novel poly(vinyl formal)‐based single‐ion‐conductor polymer electrolytes

“…Additionally, Figure (a,b) also shows that both M ′ and M ″ increased with temperature; this was attributed to the faster mobility of Li + ions and decreased relaxation time of SCP‐1.0 with increasing temperature. The results indicate that the relaxation was thermally activated and charge carrier hopping occurred at a certain temperature; this was in agreement with the report by Furlani et al . in which the ions appeared to be bound as ion‐pair dipoles on short timescales, whereas at least one in each pair was free to move during longer timescales and gave rise to σ.…”

AC and DC conductivity correlation: The coefficient of Barton–Nakajima–Namikawa relation

“…(4) are equal not only at the high frequency limit but also at ω = ω 0 , then in these cases, from Eqs. (2), (3) and (4) with ω = ω 0 we find σ 0 = ε 0 ω 0 ε ′′ (ω 0 )/2 (5) and…”

Dielectric spectroscopy and confirmation of ion conduction mechanism in direct melt compounded hot-press polymer nanocomposite electrolytes

“…6). Recently, Furlani et al [43] confirmed the strong correlation between the dielectric relaxation times, relaxation strength and ionic conductivity in lithium-doped PEO of average molecular weight 400 g/mol based electrolytes at ambient temperature. The small amount of MMT in PEO matrix significantly increases the mechanical and thermal strength of the PEO-MMT nanocomposite materials [10,16].…”